Support for S/MIME-Signed Emails

Many organizations rely on S/MIME (Secure/Multipurpose Internet Mail Extensions) to digitally sign and encrypt emails. S/MIME uses digital certificates to:

  • Verify the sender's identity

  • Ensure the message content remains unchanged during transit

Digitally signed emails provide recipients with assurance of the message's authenticity and integrity.

However, standard email security actions - such as adding banners, rewriting URLs, or removing potentially risky attachments - can unintentionally alter these messages. Such modifications may invalidate the digital signature and trigger warnings for recipients.

Preserving Signature Integrity in S/MIME-Signed Emails

To help maintain the integrity of digitally signed messages, Avanan offers the ability to avoid security modifications for S/MIME-signed emails. When enabled, this feature allows these messages to be delivered without alterations, preserving both the digital signature and the original message structure.

Note:

  • Skipping security modifications may reduce protection for the affected messages. Enable this feature only when message integrity takes precedence over certain security controls.

  • This feature is available by request only. To enable it, contact Avanan Support and request activation of the S/MIME skip-modification option.